Mapping Invasive Plants

Mapping Invasive Plants with Drones and Satellite Images

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Invasive plant species can alter the composition, structure and functioning of terrestrial ecosystems, especially in a place with fragile ecosystems, like the Galapagos Archipelago. To support the conservation of Galapagos and to optimize resources for the management of these invasive plants, we need to know their distribution and abundance. Therefore, we are creating high resolution maps of invasive plants in the humid zone of Galapagos. To achieve this, we are using remote sensors, such as satellite images and drones, which enable us to cover large areas that are difficult to access.

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Project Details

Video on the mapping of invasive plants in Galapagos.

How did we do it?

We mixed a bit of fun flying drones in the fresh air of the Galapagos highlands with many cups of coffee, as we worked on programming tasks behind the computer, to arrive at the perfect recipe for the mapping of invasive plants.

For the mapping we are using cutting-edge technology. Our main resources are aerial photos captured with drones (DJI Inspire 1 and Mavic Pro) and satellite images with very high resolution (WorldView-2), donated by the DigitalGlobe Foundation, through Brown University. The photos captured by drones are very detailed, which allow us to visually identify and delineate the plant species present in our sampling area. While the WorldView-2 satellite images have a lower resolution than the drone photos, their potential lies in the fact that they cover the entire study area and are multispectral. This means that they have eight color channels (instead of four as the Google Earth satellite images). Among those eight spectral channels, there are some which cover the infrared range, which is very useful for characterizing plant species with different concentrations of chlorophyll. Combining the information captured with the drone with the color information in the satellite image, we train a statistical model called “Random Forest”. This model identifies a species based on its color characteristics and then extrapolates this information to the entire satellite image. This way, an approximation of the spatial distribution and abundance of each species is being attained.

Diagram of the applied methodology. Based on the photos captured with the drone, individual species are identified and delineated. The delineated shapes are then applied to the multispectral satellite image. A classification model based on the color characteristics of each species is created. This model will then be applied to the entire satellite image. Map elaborated by: Carolina Carrión, CDF.

What have we achieved?

We have created maps of the distribution of the most dominant invasive plants in the humid zone of the Santa Cruz island: blackberry (Rubus niveus), guava (Psidium guajava) and Cuban cedar (Cedrela odorata). We are currently working on the maps for the islands of Floreana and Santiago, applying the same method. These maps also form a baseline to be able to determine the changes in the distribution of these invasive species in the future. We hope that this information will help the Galapagos National Park Directorate (GNPD) effectively plan management actions for invasive plants and thus contribute to the conservation of the unique species of Galapagos.

Our main goal is to have maps of the distribution and abundance of the invasive plant species in order to support conservation efforts in Galapagos.

Our results

Distribution of invasive species in the humid zone of Santa Cruz Island within the protected area:

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The “Charles Darwin Foundation for the Galapagos Islands”, in French “Fondation Charles Darwin pour les îles Galapagos”, Association International sans but lucratif (“AISBL”), has its registered office located at Chaussée de la Hulpe 177 Bte 20 (rez) - 1170, Brussels, and is registered under the trade registry of Brussels under the number 0409.359.103.